Here's an old chestnut: why, if people's attitudes towards the environment are (in general) positive, and if levels of concern about climate change are consistently high, don't these attitudes translate into meaningful behavioural changes?

Answers to this question typically cite financial and motivational barriers that create an attitude/behaviour gap, or the lack of infrastructure, for example, public transport, required for people's low-carbon intentions to become a reality.

However, a new study released this month suggests a different answer – the views that people express in opinion polls may not actually be the best guide to what they really think about climate change and sustainability.

Using the Implicit Association Test (IAT), developed in the 1990s and now widely used in social psychology, Geoffrey Beattie and Laura McGuire at Manchester University asked whether people's "explicit" attitudes (the responses people give in surveys and opinion polls) or their "implicit" attitudes (which can only be revealed by people's reaction times on a specially designed task) best predicted the amount of attention they paid to iconic images of climate change.

The basic premise of the IAT is that if two concepts are strongly associated in someone's mind, then they will be able to quickly and correctly categorise them in a computer task (whereas concepts that are less strongly associated will take longer to process).

Beattie's previous research found that people's explicit and implicit attitudes towards climate change and low-carbon products do not always match, suggesting that some people may not be as green as they say they are. But in their new study, Beattie and McGuire took this argument one step further.

Participants were asked to rate how much they agreed with statements such as: "I prefer a product with a low carbon footprint". But they also completed an IAT where they had to assign a series of positive or negative terms to the target category of "low carbon footprint". The researchers then showed them a series of images, some of which were iconic negative images of climate change (for example, a stranded polar bear), some of which were positive images of nature (for example, a field of sunflowers), and some of which were everyday household objects. Intermingled across a series of slides, participants could choose which images to look at.

The results were striking: only implicit attitudes predicted how long people looked at iconic images of climate change. It did not matter if people had expressed a positive explicit attitude towards low-carbon products. Only people with strongly positive implicit attitudes (ie the people with quick reaction times between positive terms and the low carbon footprint category) chose to linger on the climate change images.

These findings suggest that even people who express a high degree of concern about climate change, or who claim a great deal of interest in low-carbon products, may actually be unconsciously shielding themselves from imagery associated with climate change and by extension, a deeper reflection on how to change their behaviour in response to it.

As Beattie and McGuire put it: "People can choose not to go to the cinema to watch An Inconvenient Truth, people can ignore television documentaries on climate change, people can fail to attend to images of climate change – and this whole process does not have to be conscious either."

They add: "What happens if you never see the evidence for climate change? What hope for the planet then?"

Beattie and McGuire's study suggests that we cannot necessarily trust survey findings to tell us the full story about people's views on climate change and sustainability. But although implicit attitudes may paint a more complex picture about public perceptions of climate change and sustainability, psychological research is also starting to reveal what influences people at the implicit level.

For example, one study asked people to associate themselves with a particular brand of drink rather than another, and then looked at how this influenced their scores on the IAT. Implicit attitudes became more positive when people believed that the drink in question was linked to their self-concept – the kind of drink that someone like them would buy.

So making sustainable behaviour something that is linked to people's self-identities, rather than simply a series of unrelated, disjointed actions, can increase the chance that people will act sustainably across a range of different situations. Perhaps one way in which developing a green self-identity manifests itself is through increasingly sustainable implicit attitudes.

And it is these hidden thoughts – rather than the views measured in opinion polls – that may hold the secret to deepening public engagement with climate change and sustainability.